I. Field of the Invention
The present invention relates to an intake system for a V-type multi-cylinder internal combustion engine and more specifically to arrangement of some constituent parts of an intake system in the space between the rows of cylinders of a V-type multicylinder internal combustion engine.
II. Description of the Prior Art
An example of a prior art intake system for a V-8 internal combustion engine is shown in FIGS. 10 to 12.
Referring to the figures, intake air having passed an air cleaner (not shown) is conducted through an air duct 11 to a throttle chamber 10, then controlled in flow rate by a throttle valve 10a disposed in the throttle chamber 10 and flows into a surge tank or collector housing 1. The intake air having reached the collector housing 1 is drawn through independent intake passages or pipes 2-9 of substantially the same length and through respective intake ports 13 formed in a cylinder head 12 to respective cylinders 16. The reason why the intake pipes 2-9 are constructed so as to be of substantially the same length is for avoiding variations of the charging efficiency from cylinder to cylinder.
Fuel injectors 20 are installed on the curved portions of the intake pipes 2-9 adjacent the intake ports 13 and inject fuel toward intake valves 14. The injected fuel is mixed with intake air conducted thereto from the collector housing 1 through the intake pipes 2-9. The intake air/fuel mixture is supplied into the cylinders 16 and ignited at predetermined timings to burn, whereby to cause pistons 17 to reciprocate. After combustion of the mixture, the exhaust gases are discharged through exhaust ports 18 and exhaust valves 19 and through, though not shown, an exhaust purifying device and silencer to the open air.
In the meantime, 46 in FIGS. 10 and 12 is an alternator disposed at an end of the rows of cylinders of a V-8 internal combustion engine, and indicated by l in FIG. 10 is the distance between the collector housing 1 side end of the alternator 46 and the center of the cylinder 16 nearest the alternator 46.
By disposing some constituent parts of the intake system between the rows of cylinders of a V-type multi-cylinder internal combustion engine in the above described manner, it becomes possible to make the most of the characteristic features of the V-type multi-cylinder internal combustion engine, i.e., it becomes possible to make the engine of itself more compact and the overall height and length of the engine smaller as compared with a comparable in-line multi-cylinder internal combustion engine. For this reason, it is a usual practice to utilize the space between the rows of cylinders for arrangement of some constituent parts of the intake system.
FIG. 13 shows another prior art arrangement in which an elongated collector housing 1 is disposed so as to longitudinally extend across the rows of cylinders at substantially the center thereof and at right angles and provided with a plurality of openings the number of which are half the number of the cylinders and in which throttle valves 10a are disposed. The intake pipes are bifurcated at the portions downstream of the throttle valves 10a into pipe portions 2-9 which are communicated with the respective cylinders as disclosed in Japanese provisional patent publication No. 61-265347.
In the arrangements described above, the intake pipes are needed long in order to attain an efficient inertia charge at low speed. When, however, the collector housing 1 is disposed in the space between the rows of cylinders as shown in FIGS. 10 to 12, the collector housing 1 occupies most of the space between the rows of cylinders, thus making it impossible to arrange other engine accessories as an alternator, etc. between the rows of cylinders. Further, in order to make longer the intake pipes within a limited space surrounded by the cylinders in rows and the surge tank, it is necessary to provide a number of curved portions to the intake pipes, resulting in an increased flow resistance.
Further, in order to increase the lengths of the intake pipes without causing substantial increase of the overall all height of the engine and the flow resistance, it will be considered to make the collector housing 1 thinner for thereby increasing the distance between the collector housing 1 and the intake ports 13. However, this naturally results in an insufficient volume of the collector housing 1.
In this connection, as shown in FIG. 13, by disposing the collector housing 1 so as to longitudinally extend across the rows of cylinders at substantially the center thereof and at right angles, the space between the rows of cylinders is not largely occupied by the collector housing 1 and therefore it can be attained relatively with ease to increase the lengths of the intake pipes. However, since the intake pipes 2-9 are arranged so as to extend from the bottom of the collector housing 1 separately, the collector housing 1 is positioned relatively high above the cylinder head, thus increasing the overall height of the engine and therefore making it impossible to make the most of the characteristic features of the V-type multi-cylinder internal combustion engine.